Apparatus for brazing a heat exchanger

ABSTRACT

An apparatus for brazing a heat exchanger, in particular a flat-tube heat exchanger, comprising a block of flat tubes and corrugated fins. The apparatus comprises a brazing frame that accommodates a tube-fin block within itself and which has two brazing bars arranged parallel to each other which are connected by tie rods. The brazing bars have a plurality of openings that are open toward one side, e.g., notches.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a divisional of U.S. application Ser. No.10/626,863, filed Jul. 25, 2003, the entire contents of which isincorporated herein by reference.

European Priority Application 02 291 895.7, filed Jul. 26, 2002,including the specification, drawings, claims and abstract, isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of heat exchangersand methods and apparatus for manufacturing heat exchangers. Moreparticularly, the invention relates to an apparatus for brazing a heatexchanger, in particular a flat-tube condenser. According to anotheraspect, the invention relates to a method for brazing a heat exchanger,and in accordance with yet another aspect, the invention also relates toa heat exchanger.

Heat exchangers, in particular, flat-tube condensers, are used for motorvehicle air-conditioning systems. Heat exchangers of this type arepredominantly produced from aluminum alloys and are made by brazing in abrazing furnace. Such flat-tube condensers—as known, for example, fromDE-A 42 38 853—comprise a heat transfer network or block, which is builtup from a large number of flat tubes and corrugated fins arrangedbetween the tubes, and manifold or header tubes, into which the flattubes open. The production of a flat-tube condenser built up in this wayis carried out in that, first of all, the parts for the block, that isto say the flat tubes and corrugated fins, are joined mechanically (theyare “blocked”) in a corresponding machine, which is known as the blockproducer. In order to achieve satisfactory brazing of the corrugatedfins to the flat tubes, the assembled block is clamped transversely withrespect to the longitudinal direction of the tubes, in order that allthe corrugations of the corrugated fins rest uniformly on the flattubes. In this clamped or compressed state, the block is moved into thebrazing furnace, while being held in a brazing apparatus, and is brazedthere. When the brazing temperature is reached, the brazing materiallocated on the fins and/or tubes is melted and the entire block “isset.” Then, following brazing, the heat exchanger can be removed fromthe brazing apparatus after it has cooled to at least some degree.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a brazing apparatuswhich comprises few parts, is simple in construction and easy to handle.

It is also an object of the invention to provide an improved method forbrazing a heat exchanger of the type mentioned above, preferably to theeffect that the sequence of method steps for the block production issimplified insofar as brazing is concerned. Also, preferably theproduction costs of the heat exchanger are reduced.

Another object the invention resides in the provision of an improvedheat exchanger made according to the method of the invention.

In accomplishing the foregoing objects of the invention, there has beenprovided in accordance with one aspect of the invention an apparatus forbrazing a heat exchanger that includes a block of tubes and fins, whichcomprises: a brazing frame which accommodates the block within itselfand which comprises two brazing bars arranged parallel to each other anda plurality of tie rods which connect the brazing bars together.Preferably, the brazing bars are at a fixed distance b from each otherwhich corresponds to a width B of the block in a compressed conditionsuitable for brazing. More preferably, the brazing bars have an openprofile which opens toward one longitudinal side and which comprises aplurality of openings therein.

In accordance with another aspect of the invention, there has beenprovided a method for brazing a heat exchanger that includes a block oftubes and fins, comprising: mechanically joining the tubes and fins toform a block; transversely compressing the block with respect to thelongitudinal direction of the tubes to a width dimension B; insertingthe block into a brazing frame which has a fixed lateral dimensionsufficient to maintain the block in a compressed state suitable forbrazing; and brazing the compressed block, while held in the brazingframe, in a brazing furnace.

Further objects, features and advantages of the invention will becomeapparent from the detailed description of preferred embodiments thatfollows, when considered together with the accompanying figures ofdrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary preferred embodiment of the invention is illustrated in thedrawing and will be described in detail below. In the drawing:

FIG. 1 is a perspective view showing brazing apparatus; and

FIG. 2 is a similar view of the brazing apparatus according to FIG. 1,with a block inserted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One advantage of the brazing apparatus according to the invention isthat the tube/fin block is inserted into the brazing apparatus in thecompressed state and can be moved into the brazing furnace together withthe brazing apparatus, without further parts being needed for clampingthe block (a clamping device) for this purpose. The brazing apparatuscomprises a single part, that is to say without any further loose parts.The block can be removed from the brazing apparatus without any aids ortools after brazing.

In order to perform the clamping of the compressed block, two oppositebrazing bars belonging to the brazing apparatus are connected to eachother by tie rods. The result is uniform pressing and contact betweenthe corrugated fins and the flat tubes.

The two brazing bars advantageously have a profile which includesopenings on at least one longitudinal side. Thus, both opposing brazingbars are provided with openings, preferably cut-outs or notches whichare open at the top. This makes it possible for the pre-clamped block tobe inserted into the brazing apparatus from above by means of a clampingtool which has a plurality, preferably a large number, of pressurefingers that are spaced and have a size corresponding to notches. Thepressure fingers are then moved outwardly from the notches, and theclamping of the block is maintained by the brazing bars. The compressedblock can thus be inserted into the brazing apparatus without additionalaids or tools.

FIG. 1 shows a brazing apparatus 1 that can be used for brazingflat-tube condensers or heat exchangers of similar construction. Thebrazing apparatus 1 is constructed as a brazing frame and comprises twobrazing bars 2, 3 that are arranged parallel to each other and areconnected to each other by a plurality of tie rods, in this case threetie rods 3, 4, 5. Arranged transversely with respect to the tie rods 3,4, 5 are a plurality of transverse spars 6, 7, 8, which are connectedpermanently to the tie rods, for example, by means of a weldedconnection, so that the result is a rigid, distortion-free brazing frame1 having a fixed dimension at least in the lateral direction withrespect to the heat exchanger tubes of the block.

The brazing bars 2, 3 are preferably formed as flexurally rigid angledprofiles or other rail structures that ensure lateral retention.Preferably the rail structure is an angled profile having two legs 2 a,2 b and 3 a, 3 b, respectively. The legs 2 a, 3 a are preferablycontinuous, whereas the angled legs 2 b, 3 b preferably have aninterrupted shape, wherein, for example, the two mutually opposite legs2 b, 3 b preferably have a large number of slot-like notches 2 c, 3 cwhich (in the illustrated embodiment) are open at the bottom. Thenotches 2 c, 3 c are U-shaped in this exemplary preferred embodiment.Other geometric forms of notches, such as, for-example, semicircles ortriangles open to the outside are likewise possible. The brazing frame 1has the following dimensions, matched to the heat exchanger to bebrazed: length 1, height h and spacing b of the brazing bars 2, 3.

FIG. 2 shows the brazing apparatus according to FIG. 1 rotated through180 degrees, that is to say the legs 2 a, 3 b of the brazing bars 2, 3are located at the bottom here, and the notches 2 c, 3 c are open at thetop. The brazing apparatus 1 thus rests on the tie rods 3, 4, 5 on aflat support not illustrated here. A tube/fin block 9 (illustrateddashed) is inserted into the brazing frame 1, that is to say between thebrazing bars 2 b, 3 b, from above. This tube/fin block 9 is illustratedin simplified form as a box-like, flat element, specifically having alength L, a width B and a height H. As already mentioned, such a blockcomprises a large number of flat tubes and corrugated fins, of which twoflat tubes 10, 11 and a corrugated fin 12 arranged between these areschematically illustrated here by way of example. On the longitudinalsides, the block 9 is typically closed off in each case by a side part13, 14, which is constructed from flat sheet metal strips.

As already mentioned above, the block 9 is assembled (“blocked”) in ablock producer, not illustrated, and then clamped in order to press flattubes 10, 11 and corrugated fins 12 against one another. In this clampedstate, the block 9 is inserted into the brazing apparatus 1, that is tosay between the notched legs 2 b, 3 b of the brazing bars 2, 3. This iscarried out by means of two pressure tools 15, 16, which are illustratedschematically and which preferably each have a correspondingly largenumber of pressure fingers 15 a, 16 a which reach through at least someof the open spaces of the notches 2 c, 3 c.

In a preferred embodiment, the pressure tools 15, 16 therefore can becharacterized in a simplified manner as having the shape of a rake, withthe pressure fingers 15 a, 16 a forming the prongs which engage in thenotches 2 c, 3 c. The two pressure tools 15, 16 are pressed against theside parts 13, 14 of the block 9 in the direction of the two arrows P bymeans of the pressure fingers 15 a, 16 a, and in this way they hold theblock and insert it from above into the brazing apparatus 1. After theblock 9 has reached its position in the brazing apparatus 1, the twopressure tools 15, 16 are moved outwardly, that is to say counter to thedirection of the arrows P, and the block 9 is left clamped in betweenthe two brazing bars 2, 3.

Before being inserted into the brazing apparatus 1, the block 9 istherefore compressed to a dimension B, which is somewhat smaller thanthe distance b (FIG. 1) between the brazing bars 2 b, 3 b, so the block9 can be inserted with slight play. As soon as the two tools 15, 16 aremoved apart, the block 9 springs back because of the elasticity of thecorrugated fins and rests with the side parts against the notched legs 2b, 3 b of the brazing bars 2, 3. In this case, the appropriate degree ofpre-clamping of the block 9 required for the brazing process is stillmaintained.

The block 9, together with the brazing apparatus 1, is then moved into abrazing furnace (not illustrated), for example, by the brazing apparatus1 together with the block 9 being set down on a conveyor belt. Duringthe brazing process, corrugated fins and tubes are brazed to oneanother. After the brazing has been completed, the brazing apparatus 1with the block is moved out of the brazing furnace and cooled.Subsequently, the block can readily be removed from the brazingapparatus 1, since its width B has been shortened by the brazingprocess.

Although not illustrated here for reasons of simplification, the block 9can also be brazed together with bases, and/or the manifold tubes of thecondenser and/or with the manifolds and/or connecting tubes. It is onlynecessary to configure and size the brazing member in a way thatcorresponds to the final assembly of heat exchanger components that isto be pre-assembled prior to the brazing step.

The present invention has been described with reference to only a fewpreferred embodiments. Various modifications of the disclosedembodiments will be apparent to persons skilled in this field, and it isintended that the appended claims cover the invention in its broadestsense, including obvious equivalents.

1. A method for brazing a heat exchanger that includes a block of tubesand fins, comprising: mechanically joining the tubes and fins to form ablock; transversely compressing the block with respect to thelongitudinal direction of the tubes to a width dimension B; insertingthe block into a brazing frame which has a fixed lateral dimensionsufficient to maintain the block in a compressed state suitable forbrazing; and brazing the compressed block, while held in the brazingframe, in a brazing furnace.
 2. A method as claimed in claim 1, whereinthe brazing frame comprises laterally opposed brazing bars, wherein saidbars include a plurality of openings therein, and wherein the insertingcomprises inserting the compressed block by means of a compression toolhaving opposed fingers that cooperate with at least some of saidopenings during insertion.
 3. A method as claimed in claim 2, whereinsaid fixed lateral dimension of the brazing frame is less than dimensionB, and wherein the inserting comprises placing the compressed block intothe brazing frame while holding the block at dimension B, and thereafterreleasing compression on the block, whereby the block expands to equalsaid fixed lateral dimension of the brazing frame.
 4. A method asclaimed in claim 3, wherein said releasing comprises laterallywithdrawing said opposed fingers through said openings in the brazingbars.
 5. A heat exchanger produced in accordance with a method asclaimed in claim 1.